It is known that, the present photographic material developing machines and in particular of photographic paper which can be utilized in the developing and printing laboratories of large quantities of paper with different sizes and lenght, are substantially formed by a plurality of treatment tanks containing the different liquid chemical substances which are necessary to develop such photographic papers, as well as by drying units of the developed papers and by collecting containers of the developed and dried papers.
Such tanks and drying units are provided with motorized mechanical members fit to produce the unidirectional transport and feed of the phototographic paper, which is wound on a dispenser reel and placed in the loading area of the relative machine and is unwound progressively by the same and wound on a winding reel placed in the unloading area of the machine, as well as with at least a separate guide band (so called "leader"), driven by the machine motor unit and sliding into a position adjacent and parallel to the paper feed way, which band is hooked in advance on the initial zone of the paper through a grasping and dragging device (so called "pliers"), in order to produce the feed of this paper through all the developing machine. To this aim, the grasping and dragging device is substantially formed by a thin metallic plane and an extended fork, subdivided in a first portion for the winding of the photographic paper and a second portion for the hooking and the unhooking with respect to the band guide, said first portion being inserted in a correspondent groove of a cylindrical covering element, in order to produce a thin free gap between the same element and the two surfaces of the same portion, so that to insert the initial zone of the photographic paper to be dragged through the machine therein, and said second portion being provided with a bent free end portion and a torsion spring in a position opposed and spaced with respect to this bent end portion, in such a manner that the guide band can be inserted between said bent end portion and said spring, by moving this latter firstly in an opening position and then by letting it come back to its closing position in which it places itself elastically against said guide band, thereby maintaining it clamped between the same spring and the bent end portion, so that it permits to realize the dragging of the photographic paper. This fork is applied in advance on the loading area of the machine, by hooking for the sake its second portion on the guide band by operating manually on the torsion spring and by inserting the photographic paper initial zone on the first portion of said fork in the manner described above, with consequent progressive feed of the fork and of the photographic paper through all the machine. As soon as these elements arrive in correspondence at the unloading area of the same machine, the fork is unhooked automatically from the guide band through the action of an unhooking element which is wedge-shaped and applied to the machine in a position correspondent to that of the same band, in order to permit again the hooking of such fork on the initial zone of a subsequent photographic paper reel to be developed in the same manner described, while in its turn the developed photographic paper is completely wound on the relative winding reel and consequentely it can be drawn and prepared for the delivery to the customers. In practice, however, it has been found that this grasping and dragging device is critical when the photographic paper is subjected to mechanical stresses which exceed determinate values, circumstances in which the fork tends to inflect with respect to its right working position almost orthogonal with respect to the paper and guide band feed way, with consequent high stresses exerted by the same with respect to the guide band which also can produce an undesidered unhooking of such fork from said band, thereby interrupting the dragging of the photographic paper through the machine and compromising the right developing.